package com.wsx.animatordemo;

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Interpolator;
import android.view.animation.TranslateAnimation;
import android.widget.ScrollView;

/**
 * @author:wangshouxue
 * @date:2022/4/27 下午4:54
 * @description:仿微信的越界回弹效果
 */
public class BoundSV extends ScrollView {

// y方向上当前触摸点的前一次记录位置

    private int previousY =0;

// y方向上的触摸点的起始记录位置

    private int startY =0;

// y方向上的触摸点当前记录位置

    private int currentY =0;

// y方向上两次移动间移动的相对距离

    private int deltaY =0;

// 第一个子视图

    private View childView;

// 用于记录childView的初始位置

    private Rect topRect =new Rect();

//水平移动搞定距离

    private float moveHeight;

    public BoundSV(Context context) {

        this(context,null);

    }

    public BoundSV(Context context, AttributeSet attrs) {

        this(context, attrs,0);

    }

    public BoundSV(Context context, AttributeSet attrs,int defStyle) {

        super(context, attrs, defStyle);

        setFillViewport(true);

    }

    @Override

    protected void onFinishInflate() {

        super.onFinishInflate();

        if (getChildCount() >0) {

            childView = getChildAt(0);

        }

    }

    @Override

    public boolean dispatchTouchEvent(MotionEvent event) {
        if (null ==childView) {
            return super.dispatchTouchEvent(event);
        }
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                startY = (int) event.getY();
                previousY =startY;
                // 记录childView的初始位置
                topRect.set(childView.getLeft(),childView.getTop(),
                        childView.getRight(),childView.getBottom());
                moveHeight =0;
                break;
            case MotionEvent.ACTION_MOVE:
                currentY = (int) event.getY();
                deltaY =currentY -previousY;
                previousY =currentY;
                //判定是否在顶部或者滑到了底部
                if ((!childView.canScrollVertically(-1) && (currentY -startY) >0) || (!childView.canScrollVertically(1) && (currentY -startY) <0)) {
                    //计算阻尼
                    float distance =currentY -startY;
                    if (distance <0) {
                        distance *= -1;
                    }
                    float damping =0.5f;//阻尼值
                    float height = getHeight();
                    if (height !=0) {
                        if (distance > height) {
                            damping =0;
                        }else {
                            damping = (height - distance) / height;
                        }
                    }
                    if (currentY -startY <0) {
                        damping =1 - damping;
                    }
                    //阻力值限制再0.3-0.5之间，平滑过度
                    damping *=0.25;
                    damping +=0.25;
                    moveHeight =moveHeight + (deltaY * damping);
                    childView.layout(topRect.left, (int) (topRect.top +moveHeight),topRect.right, (int) (topRect.bottom +moveHeight));
                }
                break;
            case MotionEvent.ACTION_UP:
                if (!topRect.isEmpty()) {
                    //开始回移动画
                    upDownMoveAnimation();
                    // 子控件回到初始位置
                    childView.layout(topRect.left,topRect.top,topRect.right, topRect.bottom);
                }
                //重置一些参数
                startY =0;
                currentY =0;
                topRect.setEmpty();
                break;
        }
        return super.dispatchTouchEvent(event);
    }

    // 初始化上下回弹的动画效果
    private void upDownMoveAnimation() {
        TranslateAnimation animation =new TranslateAnimation(0.0f,0.0f, childView.getTop(),topRect.top);
        animation.setDuration(600);
        animation.setFillAfter(true);
        //设置阻尼动画效果
        animation.setInterpolator(new DampInterpolator());
        childView.setAnimation(animation);
    }

    public class DampInterpolator implements Interpolator {
        @Override
        public float getInterpolation(float input) {
            //没看过源码，猜测是input是时间（0-1）,返回值应该是进度（0-1）
            //先快后慢，为了更快更慢的效果，多乘了几次，现在这个效果比较满意
            return 1 - (1 - input) * (1 - input) * (1 - input) * (1 - input) * (1 - input);
        }

    }
}
